This invention relates to a vehicle restraint used to secure a truck to a loading dock. Such devices are well established in the loading dock industry. In general, these devices act as a substitute for chains and wheel chocks. A common trait is that they all employ the ICC bar of the vehicle as the means by which the vehicle is engaged and restrained. ICC bars are required by law and are placed at the rear end of the vehicle within a specified height and distance above the ground and from the rear of the vehicle. Consequently there is a limited "envelope" in which engagement with the ICC bar can take place.
Most vehicle restraints mount directly to the dock face. Typical is that illustrated in U.S. Pat. Nos. 4,264,259 and 4,695,216.
Others are mounted on the approach adjacent the dock face. Such is illustrated in U.S. Pat. No. 4,674,941. Still others, as typified by U.S. Pat. No. 5,120,181 can be mounted alternatively on the dock face or on the approach.
A third category of mounting is such where the vehicle restraint is mounted in a pit under the dock leveler, such as the "Power Hook II" device manufactured by Power Ramp or, the restraint is housed in a hole dug under the approach, as illustrated in U.S. Pat. No. 5,212,846.
Mounting the vehicle restraint in front of the dock leveler, whether to the dock face or onto the approach is less expensive than constructing an additional pit either under the dock leveler or in the approach sub-surface itself. However, mounting the vehicle restraint under the dock leveler has several important advantages.
First, a hook which can be mounted at the end of a long pivoting arm will travel essentially in a vertical motion without the need for complex tracks, rollers or other mechanical linkages. The ability to move in an essential vertical direction allows the restraint to capture a large number of ICC bars without binding, or becoming interlocked as the vehicle floats up and down during loading and unloading operations.
Moreover, a simple pivoting hook can have a lower height, it does not require a bulky housing and thus can reach lower ICC bars than other mechanisms. For example, a device as such as that illustrated in U.S. Pat. No. 4,674,941, even in the retracted position, has a fundamental height associated with the mechanism. A low ICC bar might impinge that mechanism in its "at rest" position thus, preventing raising and engagement, or preventing the vehicle from approaching the dock.
A hook can also be made to retract back into the pit. Having the dock face and approach clean, without any mechanical impediments, is important to allow for the removal of snow and ice, which would otherwise impede the operation of the vehicle restraint. A hook that can retract under the dock leveler is not only protected from ice and snow but presents no obstacles to interfere with snow removal. It is also important to allow the dock to be used by vehicles having special equipment, such as a hydraulic elevating tail gate. Conventional vehicle restraints mounted to the dock face may prevent such vehicles from approaching the dock.
Pit mounted vehicle restraints utilizing retractable hooks are known ("Power Hook II"). However, the restraining force in those units is carried by hydraulic cylinders. That is, the technique of extension and retraction is via hydraulics. This makes such units expensive and requires them to be used in conjunction with an hydraulic dock leveler.
Moreover, the pit for the vehicle restraint will also collect dust debris and is generally hard to clean.